


Appetisers

by Askellie



Series: Leviathan AU [1]
Category: Undertale (Video Game)
Genre: Alternate Universe - Merpeople, Bad Sanses | Nightmare's Gang (Undertale), Blood and Gore, Crosstale Sans (Undertale), Dreamtale Nightmare Sans (Undertale), Dreamtale Sans | Dream (Undertale), Dusttale Sans (Undertale), Ecto-Tentacles (Undertale), Feeding Kink, Grooming, Horrortale Sans (Undertale), Killer Sans (Undertale) - Freeform, Kracken Nightmare, Leviathan AU, M/M, Shark-Mer Cross
Language: English
Status: Completed
Published: 2021-02-09
Updated: 2021-02-09
Packaged: 2021-03-15 06:07:42
Rating: Mature
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,339
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/29309307
Author URL: https://archiveofourown.org/users/Askellie/pseuds/Askellie
Summary: Cross learns how to feast like a real mer-shark while being courted into the shiver.[Based on Skumhuu's Leviathan AU]
Relationships: Sans/Sans (Undertale)
Series: Leviathan AU [1]
Series URL: https://archiveofourown.org/series/2152734
Comments: 17
Kudos: 257





	Appetisers

“We’re back!” Killer calls in cheerful sing-song -- an entirely unnecessary announcement since the cloud of blood surrounding the hunting party preceded them long before the sound could carry into the grotto. Cross’s gills tingle as the scent grows irresistibly thick even as the memory of Gaster’s disapproval brings a mirror of distaste to Cross’s own expression. Still, he can’t help but drift down from his guard perch to see what the shiver has brought in.

The glee in Killer’s voice is wholly justified. Horror is carrying a pair of sleek, sumptuous marlin, one under each arm, their throats still misting with blood where they were neatly torn open. Killer has an enormous tuna balanced across his back, its heavy, limp body held in place by an old length of rope likely pilfered from one of the sunken ships. Dust’s load is lighter, but more varied, with woven pouches of seaweed full to bursting with clamshells and the tendrils of cephalopods. Cross can only imagine they’re for Dream, who prefers smaller, sweeter prey and doesn’t seem to mind eating creatures in the likeness of his brother. 

The water of the cavern shifts, stirring the bloody water like a tempest as Nightmare unfurls from the deepest part of the cavern, the eerie glow of his eye bathing the space in bright teal light. Killer emphatically sloughs off his carcass, dropping it to the grotto floor so he’s free to sidle closer to Nightmare’s looming form, his tail flicking back and forth like an excited pup. 

“Hey boss! Look what we got!”

“Looks like you had a very successful hunt,” Nightmare observes. Even using his softer tones, his voice thrums between Cross’s ribs like the resonance of an underground tremor. It still strikes a faint note of alarm in Cross, but Killer only beams and fearlessly drapes himself across Nightmare’s offered hand. He shamelessly accepts the reward of a firm, approving stroke down the length of his spine and tail before impatiently wriggling free. He saunters back to where Horror and Dust have also unloaded their catches into an enticing banquet spread across the sand. Cross’s mouth is watering, his attention so fixed on the meat that he startles when Dream brushes against him. His spluttering chirp of surprise makes the smaller mer giggle.

“There’s so much today!” Dream says, his eyelights gleaming with delight. “You’re going to eat with us this time, aren’t you, Cross?”

Cross balks immediately, swallowing back the traitorous pang of phantom hunger. He doesn’t _need_ to eat, it’s just the compelling smell of blood in the water tricking him into thinking he does. He’s spent years learning to control himself, and he can fight the urge if need be. Besides, he didn’t contribute to this hunt. Even with the generous quantity on offer, there’s enough mouths to feed without Cross taking an undeserved share.

Only his refusal somehow sticks in his throat when Dream takes his hand. His hold is gentle and undemanding, but somehow Cross feels like a helpless captive as he’s drawn unerringly closer to the ring of fresh kills.

“No sense in letting it go to waste,” Dream tells him reasonably. “Ohh, look! It’s one of the stripey ones!”

Fearlessly, he reaches around Dust and pulls the body of an eel out from under his nose. Instead of a territorial snarl, Dust only gives a small scoff and a derisive, “The pattern doesn’t make them taste any better.”

“But they’re pretty,” Dream argues. Despite his appreciation, it doesn’t stop him from gouging his fingers into its back, tearing off a thick chunk of its side. “Here, Cross, have you tried one of these before? They’re good.”

Cross tentatively takes the bloody strip, feeling the smoothness of the striped skin and the delicate grain of the meat. He hesitantly brings it to his mouth, feeling heavily scrutinised even though the rest of the shiver is absorbed in sating their own appetites. Dust has claimed one of the marlin, tearing vigorously into its already butchered throat while Killer and Horror are fighting over the belly of the tuna, arguing about the best way to split it. Cross risks a covert glance at Nightmare only to find that single, enormous eye turned on him like a spotlight. Hastily, he turns away, feeling furtive and guilty as he shoves the small morsel into his mouth.

It’s rich and salty on his tongue. The meat is almost overpoweringly fresh, nothing at all like the painstakingly drained and preserved rations he’s learned to make for himself. The flavor makes his eyes burn with some swell of emotion he can’t quite identify. Nostalgia, maybe? He hasn’t eaten something like this since he was a small pup himself.

“It’s good,” he says to Dream’s expectant look, gulping it down along with the unexpected lump in his throat.

“The yellow ones are better,” Dust injects, lifting his bloody face away from his meal. Brusquely, he plucks the body of a pale colored eel from the pile and tears off a strip of its flesh. “They’re thicker. Fattier.”

The chunk of meat is thrust roughly into Cross’s hands, and he takes it on reflex. Dust has already turned away, his expression obscured, making it even harder to know how to feel about the unexpected offering. Cross looks down at the fresh gore smearing across his fingers, and for an absurd moment he wants to keep it, cherish it, rather than eat it, but that would be a waste. He brings it to his mouth, only to nearly choke as Killer suddenly pounces on his back mid-swallow. 

“Eels are smallfry. You should try eating a _real_ catch,” Killer declares while Cross frantically struggles to dislodge the meat caught in his throat. He gestures emphatically to the other marlin, which is slightly larger than the one Dust chose. “This one over here...she put up a good fight.”

“The better they fight, the better they taste,” Horror agrees, having won the argument over the tuna. He’s cradling it in his arms with all the care and appreciation of a lover, but when his mouth skims the fish’s jaw it comes away sticky and red.

“I took her down myself,” Killer says proudly, ignoring the faint scoff from Dust. “So it’s obviously the best. See for yourself!”

Rather than tearing off a polite strip, Killer drags the entire carcass up with easy strength and offers its tender underbelly to Cross in blatant encouragement. Cross stares, momentarily taken aback by the simple but unthinkable idea of taking a bite straight from the corpse itself.

“But I didn’t...” he fumbles, words tripping clumsily over each other as his teeth tingle with urgent want, “It’s yours, I can’t-”

Killer’s hand curls around the back of his neck, unerringly drawing Cross closer to the corpse until his nasal bone is bushing against its pelvic fins. “Sure you can. It’s mine, so I get to choose who I share it with. So come on, have a little taste…”

Cross’s soul is hammering against the underside of his sternum. He tells himself it’s from the faint prickle of Killer’s claws against his nape and the ambiguous implication that it would be rude to refuse. It’s not because his marrow is throbbing hotly in time with his pulse, or because his instinct is screaming at him to just surrender to the demands of his-

(shivermate)

-fellow mer. Unthinkingly, Cross’s sockets drift shut as he carefully opens his jaw and lets sharp teeth sink deeply into the soft, juicy flesh. It ignites on his tongue like the flare of a falling star, bright and brilliant and mesmerising. With a soft groan he reaches out and blindly scrabbles for a hold, hands finding purchase on Killer’s hips as he bites down again, tearing a wider hole. Blood fills his skull through his mouth and nose, enveloping him in its heady fragrance as he loses himself in the glorious rush of feeding.

For a while, he’s not aware of anything except Killer’s hand stroking his skull and the low murmur of his voice. The words themselves are lost in a blurring haze, but the tone is crooning and full of encouragement. For the first time in weeks, Cross feels truly warm in the usually chill waters of the grotto. His marrow is humming with eagerness, and he pulls urgently on Killer’s waist, trying to bring him closer and only managing to crush the body of the marlin between them. He’s easily distracted by the slippery caress of hot entrails slithering past his chin, catching on his collarbones as the ooze free from the hole he’s torn open. Mindlessly, he turns his head and resumes gnawing on the tantalysing flesh, letting Killer’s touch guide him in stripping the fish down to its bones.

Time blurs in a euphoric haze of gluttony. It’s only when his mouth and hands register a moment of emptiness that he almost comes back to himself, whining petulantly in disappointment, but almost immediately Horror is there with a thick strap torn from the tuna. Unlike the pale flanks of the marlin, the tuna meat is dark and red, its oily surface saturating the water with the faint promise of its deliciousness. Horror’s already scraped off the scales and plucked out the pin bones as though Cross were a child or invalid liable to choke, but he can’t feel anything but helpless gratitude as he devours the smooth, perfect fillet straight from Horror’s hands. It melts on his tongue so easily he almost wonders if the water dissolved it before he could properly finish, and he licks desperately at the spaces between Horror’s carpels to chase the last traces of flavour.

He loses track of himself, moving between the writhing bodies of the Mets, from one offered mouthful to the next. He’s buried face-first in the belly of a carcass alongside Dust, their tails and fins touching and twining in a companionable dance when the warning ache in his gut finally breaks through the lustful haze of his appetite. He reluctantly pushes himself away, untangling himself from Dust and gasping in a shaky breath. The water is still murky with blood, intoxicating to his senses, but with difficulty Cross manages to crawl and bob away from the vortex of the frenzy to where the water is clean enough to start clearing his head.

He’s grossly over-eaten, that’s for certain. His entire body feels dense and cumbersome with an almost anaesthetised numbness. His stomach feels bloated and sore, but the cramping ache is accompanied by a shamefully euphoric gratification. Cross knows he’ll be useless until the feeling passes, and it’s all he can do to fight off the leaden exhaustion of overindulgence long enough to find a safe, dark passage to hide himself in.

He barely makes it half a tail-span before he’s abruptly pulled up short, yelping in surprise as his body is suddenly engulfed in the enormous coil of a tentacle. Nightmare drags him back with inescapable strength, not that Cross has any wits or will to put up any resistance. Despite the size of Nightmare’s appendage, its grip is delicate enough not to put any undue pressure on Cross’s tender, overfull stomach, leaving him squirming only in confusion rather than distress as he’s brought up towards the kraken’s judging stare.

“None of that,” Nightmare scolds when Cross tries to wriggle free, bringing up a hand to help secure his captive. “I won’t have you spreading filth throughout the cave. You need to clean up first.”

Cross’s browbones furrow in confusion, tail beating uselessly at the water. He gives a low hiss and snaps his teeth petulantly in Nightmare’s direction even though he wouldn’t dare bite the larger mer, but as his skull twists he finally catches sight of his ribs and arms and realises that the bloody swirls around him aren’t from the shiver’s feasting, but from himself. His entire torso is slicked with gore, up his arms and down his chest, even dappled along his tail in bright streaks. 

He’s mortified by the extent of it. He’s watched the others practically bathe in the viscera of their kills, feral and thoughtless as they bask in blood and entrails, but Cross has always been fastidious about his meals. He eats carefully, neatly, wasting nothing of his prey even if it means devouring the less appetising segments of gristle and cartilage. It’s almost sacrilegious not to make the most of their precious resources, but despite his disgrace Nightmare doesn’t allow him to escape.

“No, don’t move. You’re in no state to manage yourself,” Nightmare declares with an exasperated huff. A simple twist of his tentacle easily maneuvers Cross, turning him so that his belly is facing upwards. The unusual posture leaves him feeling stunned and strangely helpless. He can’t even find the will to squirm though his face is burning with shame and bewilderment. His arms and tail sag limply, and he’d simply sink to the ocean floor if not for Nightmare’s hands ascend from below, cupping beneath his body to hold him aloft.

“Hush,” Nightmare says, though Cross hasn’t made a sound...or perhaps he had: a small chuff of uncertainty, his sockets as wide and round as pearls. A thumb thicker than Cross’s humerus strokes absently across his flank. “You’ve seen me do this for the others. I won’t hurt you.”

It’s not until he’s confronted with those words that Cross realises he believes them. Despite his size, his terrifying appearance, his surly temperament, Nightmare has never once been negligent with the smaller mers under his care. He regularly insists on checking them over, especially after hunts, looking for stray wounds or unwelcome parasites that might have been overlooked in the thrill of an expedition. Since Cross has stayed mostly to the grotto, standing guard and keeping Dream company, he hasn’t required such thorough attention. He prefers to think that he’s perfectly capable of taking care of himself after so many years alone, but somehow that assurance rings hollow each time he watches Nightmare handling someone as if they’re as delicate and priceless as the treasure piled up in the deeper recesses of their home.

A small quiver wracks his body as tentacles begin to surround him, but it’s not fear he feels but a sharp pang of yearning and an equally poignant embarrassment at how blatant and pitiful his expression must be. With what little movement he can still manage, he turns his face, hiding it against the crook of Nightmare’s thumb as the long, supple tendrils curl over his body like a cocoon, pressing down in a thousand points of contact as the suckers on the underside adhere themselves across his tail and ribs. It should feel as stifling and threatening as a fisherman’s net, but instead Cross finds them oddly comforting, like a warm and weighted blanket.

He expects to feel them scrubbing at him, scraping away the blood, but instead each sucker seems to suckle on his body, a strange ripple of pressure that seems to hone in on every line of tension, gently flexing and loosening each ligament. His huff of surprise comes with a short bubble of breath, his already loose posture going even more lax and unresisting. His skull lolls to the side only for Nightmare to support it for him, expertly bracing his neck and spine as he works over Cross’s body. His tentacles feel like a hundred tiny mouths, lapping at the blood with each pinch of suction.

It may not just be his imagination. He’s seen Nightmare’s body changes at will, growing eyes and teeth and additional tentacles to suit his needs and mood. A metamorphosis that should have been horrifying, but Cross has come to regard it with more fascination than disgust. He’s often wondered how it feels -- how Nightmare feels. Are the delicate organs he makes still sensitive? Can he feel as relaxed and comfortable as Cross does right now?

Usually it’s a group effort whenever Nightmare needs his own enormous form cleaned and descaled, but the act of grooming is meant to be reciprocal, or so Cross faintly remembers from his childhood. It feels wrong to simply lie pliant and receive, so with difficulty he lifts an arm and squeezes one of the tentacles wrapped over his sternum. Its color shifts in hue, growing brighter under his touch as he fascinatedly prods and strokes its finely tapered tip. Faintly he hears Nightmare snort as if amused, but the tentacle doesn’t withdraw, patiently allowing Cross’s touch as he does his best to smooth the pebbled skin and ensure there’s no clinging algae or imperfections along its surface. 

“Brother! Aren’t you hungry?” Suddenly Dream is there, perching on the end of Nightmare’s fingers, tugging insistantly. He pauses when he catches sight of Cross, and gives a bright smile that’s only slightly marred by the flecks of blood and half-chewed scales around his mouth. “Ahh. I see you’re busy, but you shouldn’t miss out on the feast.”

“I’ll eat once you’re all finished,” Nightmare says. His deep voice sounds soft, lost in concentration. His gaze shifts only briefly towards his brother, and with a faint huff he lifts a tentacle and flicks a scale off Dream’s face. “Someone needs to clean up the mess.”

Dream’s cheeks puffed out with indignation. “I can help too!”

He leans down and licks determinedly at the corner of Cross’s mouth. One lick becomes several, each mapping the planes of Cross’s cheek and chin, lapping up the smears of blood from his messy feeding. Unfortunately, it takes only a couple of imprecise angles for Dream’s cheeks to be equally painted in gore. The bright red streaks on Dream’s cherubic face are unexpectedly enthralling, and without thought Cross nuzzles closer and licks back. It’s messy and slick, their noses bumping together as they lap clumsily at each other’s faces. A thoughtless, uncontrolled trill slips from the back of Cross’s throat but before he can feel too ashamed of it Dream answers with a sweet humm of his own. The sound burbles in the water between them, affectionate and joyful until an exasperated tentacle finally pulls them apart. 

“You’re only making it worse,” Nightmare complains, pushing Dream away. “Finish your meal. It’s your turn next once I’m done with Cross.”

Dream’s face is indeed much more stained than it was before, but his grin is bright and unrepentant even as he agrees, “Yes, brother.”

Nightmare shoos him away, his burning eyelight still focused entirely on Cross. The same tentacle that chased Dream away curls over Cross’s cheek, the suckers plucking restlessly at the planes of his mandible. “You have made quite a mess. Even Horror is rarely so careless with his meals.”

Cross wonders if he needs to burble an apology, but even as the thought takes form in his sluggish mind it’s driven entirely from his thoughts as Nightmare leans down and applies his own enormous tongue to the task of cleaning Cross’s body. The serpentine appendage is long and plush, the tip splitting into two long points that curl dexterously around him. The rough texture scours pleasantly between his ribs and along the smooth plane of his tail, sluicing away the last remnants of the feast with more aggression than the suckers. Each swipe feels like being concussed, a painless but unsettling impact that leaves Cross coated in a fine film of glistening saliva. His tail feels sleek and shiny and his bones gleam in the low light by the time Nightmare is finished, finally satisfied with the state of Cross’s cleanliness. 

“There you are,” he murmurs, fingers and tentacles stroking over Cross’s body. “Now rest, little guard. I’ll keep watch.”

There’s no possible argument against the kraken’s demand. Cross faintly feels himself being nestled against Nightmare’s side, cradled in a nest of tentacles that obligingly fold over him, giving him the tight, dark space his instincts have been craving. Hidden, safe and thoroughly cared for, Cross burrows into his new haven and drifts into blissful slumber. 


End file.
